Modern refrigeration motor-compressor units are being used in many applications wherein it is advantageous to vary the output in accordance with transient load changes. Many types of unloading systems have been proposed and employed in connection with multicylinder compressors, for selectively disabling one or more cylinders while one or more other cylinders remain operative, in order to control the output. Systems have also been employed incorporating, in place of a single unit large enough to carry the maximum load, a plurality of smaller motor-compressor units having a combined output equal to the required maximum, with means for controlling the total system in such manner as to selectively activate and deactivate less than all the compressors when it is desired to vary the output. Incorporation of a plurality of such smaller units in a single hermetic housing has also been proposed. Although such multi-unit systems are more efficient than the larger single units, in the sense that modulation can be effected without loss of efficiency, and the multi-unit arrangements can also be lower in cost, certain disadvantages have militated against their general use.
The overall object of the present invention is to provide an improved multi-unit refrigeration motor-compressor assembly incorporated in a unitary sheet metal housing and so designed that standard motor-compressor units of proven design can be employed, the arrangement being such that the housing provides a common oil sump for all units and a compartment thereabove for each unit, such compartments being substantially isolated from each other above the oil lvel but communicating with a common suction line through which gas is returned to both units from the evaporator means. Two important attributes sought by the designers of modern refrigeration equipment are compactness and quiet operation. When a plurality of motor-compressor units of a standard type are installed in their conventional upright operative position in a single sheet metal housing, it becomes necessary to so shape the housing, in order to minimize space consumption, that relatively flat walls of substantial size exist which, unless effectively stiffened or cushioned by special noise-inhibiting means, are capable of resonant vibration which tends to create objectionable noise. It will be appreciated that many methods of inhibiting noise which might readily occur to the designer would entail either a substantial increase in cost or increased size of the unit itself. For example, heavy-walled cast and/or ribbed enclosures, brazing, insulating covers, and such standard practices which might constitute obvious engineering answers to the problem involve undesirable penalties in cost and/or compactness.
In accordance with the present invention, upright motor-compressor units of types which are produced in large volume on automated production lines can be employed, and are arranged in essentially conventional fashion in the normal vertical position and relatively close together. A single sheet metal housing is fitted closely around the two units and is substantially oval in horizontal section, the side walls being flat. The central portions of the flat side walls are rigidly connected and effectively braced throughout substantially their full vertical height by a hollow chambered partitioning and stiffening member which also serves as a suction gas header or accumulator and which occupies space which would otherwise be largely unused. The partitioning member is effective to stiffen and damp resonant vibration of the side and top walls of the housing.
It will be understood from the foregoing that the objects of the invention also include the reduction of cost, noise and space, while preserving the virtues and benefits of proven designs and of proven, established manufacturing facilities and processes.
Other objects and advantages will become apparent upon consideration of the present disclosure in its entirety.